Add agent commands for self-reporting state: - bd agent state <agent> <state>: Update agent state and last_activity - bd agent heartbeat <agent>: Update last_activity timestamp only - bd agent show <agent>: Display agent bead details States: idle, spawning, running, working, stuck, done, stopped, dead Also adds AgentState and LastActivity fields to UpdateArgs in RPC protocol. 🤖 Generated with [Claude Code](https://claude.com/claude-code) Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>